14. Read the passage and answer
Michael is a student at Lincoln school in California. He is in grade 6. His school is very big and has 40 classes. Michael live with his father, mother, and his younger sister, Thorny. She is 8 years old. His parents and teacher at a high school. Michael often goes to school by the Underground. It take about 15 minutes. His classes start at 7:30 and end at 11:15. He has lunch at school with other students. In the afternoon, he play sports and learns music. He come home at 5 o'clock. In the evening, he does his homework from 7:30 to 9 o'clock. He and his family often go to bed at 10
1. Where is Michael's school?
2. How long does it take him go to school?
3. What time do his classes end?
4. What does he do in the afternoon?
5. What time does he go to bed?
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\(\dfrac{4}{x}+\dfrac{2}{y}=1\) \(\left(x;y\ne0\right)\)
\(\Rightarrow2x+4y=xy\)
\(\Rightarrow2x-8+4y-xy=-8\)
\(\Rightarrow2\left(x-4\right)-y\left(x-4\right)=-8\)
\(\Rightarrow\left(x-4\right)\left(y-2\right)=8\)
\(\Rightarrow\left(x-4;y-2\right)\in U\left(8\right)=\left\{-1;1;-2;2;-4;4;-8;8\right\}\)
\(\Rightarrow\left(x;y\right)\in\left\{\left(3;-6\right);\left(5;10\right);\left(2;-2\right);\left(8;4\right);\left(-4;;1\right);\left(12;3\right)\right\}\)
Ta có : a chia 6 dư 2 => a - 2 chia hết cho 6 => a - 2 + 12 chia hết cho 6 => a + 10 chia hết cho 6
a chia 7 dư 4 => a - 4 chia hết cho 7 => a - 4 + 14 chia hết cho 7 => a + 10 chia hết cho 7
=> a + 10 chia hết cho 6 và 7
=. a + 10 thuộc BC ( 6 ; 7 )
Mà BCNN ( 6 ; 7 ) = 42
=> a + 10 thuộc B ( 42 ) = { 0 ; 42 ; ... }
=> a + 10 chia 42 dư 42
=> a chia 42 dư 32
Vậy số a chia cho 42 dư 32
Với k = 1 ta có:
A = 6k + 5 = 6.1 + 5 = 11 (là số nguyên tố)
Vậy tồn tại số nguyên tố dạng: 6k + 5 (đpcm)
a.
Gọi x là số mol kẽm tham gia phản ứng.
\(Zn+CuSO_4\rightarrow ZnSO_4+Cu\)
x ---->x----------->x-------->x
Ta có:
\(m_{Zn}-m_{Cu}=m_{kl.giảm}\Leftrightarrow65x-64x=20-19,96\Leftrightarrow x=0,04\left(mol\right)\)
=> \(m_{Zn.pứ}=0,04.65=2,6\left(g\right)\)
b)
\(m_{ZnSO_4}=0,04.160=6,4\left(g\right)\)
a, PT: \(Zn+CuSO_4\rightarrow ZnSO_4+Cu\)
_______x_______________x_______x (mol)
Ta có: m giảm = mZn - mCu
⇒ 20 - 19,96 = 65x - 64x
⇒ x = 0,04 (mol)
⇒ mZn (pư) = 0,04.65 = 2,6 (g)
b, mZnSO4 = 0,04.161 = 6,44 (g)
Ta có: \(n_{H_2}+n_{O_2}=\dfrac{7,437}{24,79}=0,3\left(mol\right)\) (1)
- Tỉ khối của X so với H2 là 8,5.
\(\Rightarrow\dfrac{2n_{H_2}+32n_{O_2}}{n_{H_2}+n_{O_2}}=8,5.2\) \(\Rightarrow2n_{H_2}+32n_{O_2}=8,5.2.0,3\left(2\right)\)
Từ (1) và (2) ⇒ nH2 = nO2 = 0,15 (mol)
Here are the answers based on the passage:
Where is Michael's school?
How long does it take him to go to school?
What time do his classes end?
What does he do in the afternoon?
What time does he go to bed?
1 It is in California
2 It takes him 15 minutes to go to school
3 They end at 11:15
4 He plays sports and learns music
5 He goes to bed at 10